The present invention relates to apparatus for and methods of therapeutic plasma exchange wherein blood is collected from a donor and separated into constituent parts, and the donor is infused with a combination of at least one of the separated constituent parts and a replacement fluid. More particularly, the present invention relates to a single needle therapeutic plasma exchange system for alternately collecting blood from a donor and infusing the donor with a separated constituent part of the collected blood and a replacement fluid.
Automated plasmapheresis systems designed to collect a volume of whole blood from a donor, separate the blood into constituent parts, and reinfuse the donor with one of the constituent parts, e.g., packed cells, are well known. One such plasmapheresis system includes an Autopheresis-C.TM. instrument designed for use with a disposable harness set. The harness set includes a single venepuncture needle, a separator, various tubing runs and ancillary equipment. When the set is applied to the instrument and the needle is applied to the donor, the system alternates between a whole blood collection cycle and a reinfusion cycle wherein the donor is reinfused with the residual red cell concentrate. To accomplish this, the system uses pumps, sensors, clamps, transducers and other instrumentation under computer control. The donor remains connected to the system during both collection and infusion cycles until the process is completed. The system employs a membrane filter as part of the harness set and the filter yields rapid and gentle separation of whole blood into constituent parts for reinfusion and virtually cell-free plasma for collection.
More particularly, in the collection cycle of such system, whole blood is drawn from the donor through the single venepuncture needle and enters the harness set. Anticoagulant solution is pumped at a controlled rate into the blood entering the harness set. Anticoagulated whole blood is then pumped to a membrane separator, where the plasma and red cells are separated. The plasma is then passed into a collection container and the packed cells are pumped from the separator to a reservoir for subsequent reinfusion. Sensors detect the level of red cells in the reservoir and, when filled, the computer control then terminates the collection cycle and initiates the reinfusion cycle. Packed cells are then pumped from the reservoir back to the donor via the single needle. The reinfusion cycle continues until the reservoir is substantially emptied of packed cells. At that time, the system cycles to the collection cycle and continues to alternate collection and infusion cycles until a predetermined volume of plasma has been collected, at which time the system stops.
The present invention provides apparatus and methods for therapeutic plasma exchange in general and also extends the application of the aforedescribed instrument to therapeutic plasma exchange, although it will be recognized that the present invention may be useful with any fluid filtering and/or processing system wherein an input fluid is separated and infusion of a replacement fluid together with a part of the separated fluid is desired, e.g., blood processing applications.
According to the present invention, there is provided a harness set specifically configured for separation and exchange or replacement systems, i.e., a therapeutic plasma exchange system, and, more particularly configured for use with the plasmapheresis instrument previously described. The harness set preferably includes a single venepuncture needle, a plasma membrane separator, a reservoir, a fluid replacement container, an anticoagulant container and a plasma collection container. These various elements are connected by various tubing runs, i.e., lines or conduits. Thus, when the harness set is applied to the instrument, blood may be withdrawn from the donor through the venepuncture needle. An anticoagulant is added to the blood and the anticoagulated blood flows through the separation device, where it is separated into blood constituents, i.e., a plasma and packed cells. The plasma flows to the plasma collection bag and the packed cells flow to the reservoir. The harness set is constructed for application to the instrument such that, during the collection cycle, the blood collection pump pumps blood from the donor to the separator and the cell pump pumps packed cells into the reservoir.
When a predetermined quantity of packed cells have been stored in the reservoir, the collection cycle is terminated and an infusion cycle is initiated to mix the packed cells and the replacement fluid one with the other and return those fluids to the donor through the single venepuncture needle. During the infusion cycle, the cell pump pumps and meters replacement fluid from the replacement container through the separator for mixing with the packed cells from the reservoir whereby the combined packed cells and replacement fluid flow to the donor through the venepuncture needle. The ratio of the replacement fluid rate to the packed red cell rate returned to the donor can be controlled from zero to a desirable maximum. That maximum is defined such that the replacement rate does not exceed the blood pump rate so that flow of replacement fluid into the reservoir is avoided. This ensures that the optical sensors on the instrument for determining the packed cells level in the reservoir remain effective. It will be appreciated that the optical sensors provide input to the computerized instrument control to advance the system from the collection cycle to the infusion cycle when the reservoir is filled with packed cells and, when the reservoir is emptied of packed cells, to end the infusion cycle and begin the next collection cycle.
In a preferred embodiment hereof in accordance with the present invention, there is provided a plasma exchange system for separating blood received from a donor into constituents and infusing the donor with a first blood constituent and a replacement fluid, the system being comprised of a separator for separating first and second blood constituents from whole blood, a reservoir for containing blood and having a single port and a single venepuncture needle for supplying whole blood from the donor to the separator during a whole blood collection cycle and infusing the donor with a blood constituent and a replacement fluid during an infusion cycle. Means are provided for supplying a first blood constituent from the separator through the port to the reservoir during a collection cycle, the means including the single venepuncture needle in communication with the reservoir through the port for flowing the first blood constituent in the reservoir to the donor during the infusion cycle. Also provided is a fluid replacement supply source and means in communication with the fluid replacement supply source and flow means for supplying replacement fluid to the donor during the infusion cycle.
In a further preferred embodiment of the present invention, there is provided a method for separating blood received from a donor into constituents and infusing a donor with a first blood constituent and a replacement fluid, comprising the steps of supplying whole blood from a donor to a separator during a blood collection cycle, separating the whole blood into constituents and storing at least a first blood constituent in a reservoir for reinfusion into the donor and, during an infusion cycle, pumping replacement fluid through the separator, pumping the first blood constituent from the reservoir, mixing the first blood constituent pumped from the reservoir and the replacement fluid from the separator one with the other, and infusing the donor with the combined first blood constituent and the replacement fluid.
Accordingly, it is a primary object of the present invention to provide novel and improved apparatus and methods for therapeutic plasma exchange wherein whole blood may be separated into constituent parts and one of such parts may be readily and easily combined with a replacement fluid for infusing the donor.
These and further objects and advantages of the present invention will become more apparent upon reference to the following specification, appended claims and drawings.